Gosick

The year is 1924, the place, Sauville, a small European country neatly tucked beside the Alps... Kazuya Kujo has been studying abroad at the prestigious Saint Marguerite Academy, where urban legends and horror stories are all the rage. Most Kazuya ignores -- but the story of the "Queen Berry", a mysterious ghost ship, really gets to him. Of course, his brainy friend Victorique is much more intrigued by true stories, and she uses her unrivaled logic to solve mysteries even the town's famous detective can't. Ironically, it's Victorique's inquisitive nature that leads the duo to board a ship that matches the "Queen Berry"'s description to a tee, a ship that might just hold the key to solving a sinister mystery... Kazuki Sakuraba's modern twist on Holmes and Watson-- pairing Victorique, a brittle young girl with doll-like looks with her eager-to-please sidekick Kazuya-- make this international bestseller a must-read murder mystery. (Source: TOKYOPOP)

Kujo Kazuya is studying abroad in Sovuria (a fictional country in Europe), where he meets the mysterious Victoria. Possessing a brilliant mind, which she calls "fountain of wisdom", she seems to know everything, although she never attends classes and is restricted to her room and the schools library. (Source: taken from the light novel summary) Note: Volume 2 contains the extra "Suigyo no Majiwari" (水魚の交わり).